The present invention relates generally to apparatus for binding bales with a filament, such as baling wire, and more particularly, to apparatus wherein the binding filament is automatically wound around the bale and then twisted to secure the filament to the bale. The apparatus of the invention is of the type wherein the bales to be bound are formed in a press chamber by means of a press die with at least one loop of baling wire arranged to extend within a winding plane being applied to each bale. The apparatus includes a twisting head which twists the ends of the binding filament together in order to secure the filament around each bale with the twisting head being mounted for pivotal movement into and out of twisting position.
Inasmuch as the wire or filament which is used in devices such as the present invention must be twisted at its ends in order to secure the wire to the bale to be bound, the forces which develop within such binding filaments tend to cause rupture of the filament during the twisting operation. In the prior art, devices of this type have been known wherein attempts have been made to avoid disadvantages caused by overstressing of the binding filament caused by the twisting of the filament which may result in frequent breaks in the filament. Such a device is, for example, disclosed in German DOS No. 2, 419,151. Although this device operates satisfactorily, occasional wire breaks cannot be avoided. In the operation of this device, a twist zone is formed during the twisting of a pair of wires by a twist wheel. The two wires to be twisted together extend above and below the twist wheel over a given distance. The twist wheel includes a radially extending slot within which the wires to be twisted together are inserted with rotation of the wheel causing the wires to twist. The slot in the twist wheel generally is formed with a width which is less than the thickness of the twist zones. Since the width of the slot corresponds substantially to the thickness of a wire, displacement of the wire in the axial direction cannot be accommodated immediately after the start of twisting. On the other hand, since the length of wire to be twisted is shortened during the twisting operation, tensile forces and thus wire breaks cannot be avoided unless compensation is provided for the shortening of the wire.
Generally, the baling wire to be used is delivered from supply rolls. Since the supply rolls freely dispense wire, when the twisting operation is performed, the side of the twist facing or closest to the supply rolls generally causes no problem inasmuch as any tensile forces which are developed will be alleviated merely by further dispensing of wire.
However, since the wire must be wrapped around a bale, one side of the twist, or the side thereof opposite the side facing the supply rolls, will have no ability to compensate for tensile forces since that side of the twist will be firmly engaged around the bale. Thus, where the loop of wire extending around the bale is produced only with enough wire to provide a loop circumference to accommodate the girth of the bale, no compensation for shortening of the wire due to the twisting operation is possible. Compensation for the aforementioned forces caused by shortening of the wire is only possible if the bale to be bound is loosely engaged by the encircling wire. Of course, such a loose binding of the bale is undesirable.
Depending upon the material from which the bale is made, and depending particularly upon the elasticity or resilience of the material, greater or lesser tensile forces will be developed in the baling wire causing breaks therein. Particularly with bales made of very hard material, breaks will occur very close to the twist zone between the twist zone and the twist wheel forming the twist.
When a break occurs, the bale of material may be inadequately bound and as a result such bales involving broken binding filaments must be taken out of production thereby leading to interruptions in the continuity of the baling operation.
In addition to this, an inflexible twist zone in a binding filament will produce an adverse effect inasmuch as the resulting high tensile stresses generated will influence both the bearing of the twist wheel and the suspension of the twisting head causing premature wear of these parts.
The present invention is directed toward the problem of developing a device for overcoming the aforementioned difficulties. The invention is directed toward providing means for reducing or eliminating the potential for breakage of a binding filament in apparatus for winding bales with wire. Furthermore, the invention, by reducing the adverse forces generated during the baling process, operates to extend the life of the apparatus and particularly the life of the twisting head or wheel.